Kant's Conceptual Scheme: Criticisms

We only know, a priori, features of the world as we actually perceive it.

Because we receive data which is filtered through the conceptual scheme, we cannot be certain that our concepts accurately (or even inaccurately) apply to the real world.

As a result, Kant cannot claim that we have knowledge of the noumenal (real) world, because we only have access to the phenomenal (concept-filtered) world. As such, does the conceptual scheme really provide us with synthetic a priori knowledge? The answer seems to be no. If the conceptual scheme ultimately only provides us with a subjective view of the real world, then surely we cannot claim to know anything about the real world at all.

To illustrate: All our sensations appear to us in space and time. But we cannot know whether or not space and time truly exist in the real world. For all we know, the world might not be spatio-temporal at all, and the mind may simply be applying the concepts of space and time to the world in order to make it intelligible.

We can't actually comprehend a world without space or time (and, arguably, we can't comprehend a world lacking other concepts proposed by Kant) - we can only imagine that which has basis in what we have already experienced. As a result, Kant suggests that we should call the phenomenal world (the world we actually experience) the real world, because it is the world we inhabit,…